FIRST REPORT OF MIXED INFECTION OF PAPAYA RINGSPOT VIRUS AND PAPAYA LEAF DISTORTION MOSAIC VIRUS ON CARICA PAPAYA L
W. Shen, D. Tuo, Y. Yang, P. Yan, X. Li, P. Zhou
Papaya ringspot virus (PRSV) and Papaya leaf distortion mosaic virus (PLDMV) from the family Potyviridae produce similar symptoms in papaya such as foliar mosaic, ringspots and distortion, water soaking streaks on petioles, and ringspots on fruit. PRSV is the most widespread and destructive viral disease damaging papaya production in the world, whereas PLDMV was recently identified in China (Tuo et al., 2013). In March 2014, 23 papaya trees displaying disease symptoms similar to those of PRSV or PLDMV were observed in Haikou (Hainan Island, China). Six samples were co-infected with PRSV and PLDMV, as shown by DAC-ELISA with antisera to PRSV or PLDMV. Mixed infection was subsequently confirmed by RT-PCR using PRSV-specific primers designed in a highly conserved region of gene P3 (P3-F, 5′TTGTGTACGACTTCTCACCGAA3′ and P3-R, 5′CGAATGTCATCCAAAGACT GATGATAAAC3′) and PLDMV-specific primers designed in a highly conserved region of the coat protein (CP) gene (CP-F, 5′GGCATGTGGTTTATGATGCAAGG G3′ and CP-R, 5′GCTCCGTGTTCTCAGTCGCATT3′). DNA fragments of the expected size (613 and 355 bp, respectively) were amplified from each mixed infected sample using PRSV and PLDMV-specific primers, and then cloned and sequenced. BLASTn analysis of the nucleotide sequences obtained from the cloned PCR products showed 99% identity with a PRSV isolate from Hainan (GenBank accession No. EF183499) and 100% identity with a PLDMV isolate from Hainan (GenBank accession no. JX974555) (Lu et al., 2008; Tuo et al., 2013). To our knowledge, this is the first report of mixed infection of PRSV and PLDMV on papaya, prompting the need for evaluating the potential threat of the mixed virus infection to papaya production.